1. Field of the Invention
The present invention relates to an antenna of a communication device, and more particularly, to a metal frame being utilized as a common antenna of a communication device, for emitting and receiving radio signals of the communication device.
2. Description of the Prior Art
During product development processes of conventional communication devices, such as mobile communication products, plastic housings are mainly used by manufacturers due to cost concerns, in order to maintain basic radiation characteristics of an antenna. However, a trend of metal housing is currently brought by Apple iPhones and Macbooks. Since the metal housing has light weight, good heat dissipation, high strength, high impact resistance, good looking, anti-electromagnetic and recyclable characteristics, the metal housing is getting more and more popular. Therefore, the metal housings are mainly used in development of new generations of the mobile communication products. For example, U.S. Pat. No. 8,054,231 B2 disclosed by Ahn et al. teaches a metal case having a slot, which can be used as a slot antenna of a mobile device. But the slot may obviously ruin appearance of the metal case, and the slot needs to be arranged at a position corresponding to a specific area of the metal case. The Apple iPhone cell phone from 4 series to 5 series utilizes some of metal structural components of the cell phone as a part of an antenna for radiation. Antenna design using the metal structural components can reduce size for being arranged in a limited space. The iPhone 4 has a metal loop antenna, and the iPhone 5 has a dynamic metal loop antenna. Both of them have slits formed on the metal loop antennas, as such, antenna performance can be improved, but appearance is ruined as well.
Therefore, it is important to design a proper antenna to allow electromagnetic waves to penetrate the metal case for achieving communication purposes without obviously ruining the appearance of the metal structural components.